The sulfonation of unsaturated polymers such as ethylene/propylene/norbornene terpolymers (EPDM polymers) is well known. The unsaturation available in these polymer compositions permits facile sulfonation and the neutralized adducts have found a variety of applications. Indeed, the utility of such sulfonated polymers is generally related to their multiple ionic sites, which are capable of forming molecular associations creating a network. Unfortunately, these molecular associations in conventional sulfonated olefin polymers such as sulfonated EPDM (sulfo-EPDM), are undesirable in certain types of applications. For example, sulfo-EPDM is very effective as a viscosity modifier in lubricating oils at moderately high concentrations (cf U.S. Pat. No 3,931,021). At those concentrations, the interpolymer associations due to multiple ionic crosslinks between polymer chains make such ionic polymers much more effective as thickening agents than their nonionic EPDM precursors. At lower concentrations, however, sulfo-EPDM is found to be much less effective in thickening hydrocarbon fluids such as mineral oils. Indeed, these ionic polymers are even less effective than their nonionic polymer precursors. These results have been explained as being the consequence of intramolecular association (cf R. D. Lundberg, J. of Applied Polymer Sci., 27, 12, p. 4630, 1982).
Accordingly, it is an objective of the present invention to provide a new class of functionalized polymers that does not have multiple ionic associations.
It is another object of the present invention to provide novel sulfonated ethylene/alpha olefin copolymers.
These and other objects of the present invention will become readily understood upon reading of the invention which follows.